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What Is the Fire Triangle?

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  • Written By: Renee Booker
  • Edited By: E. E. Hubbard
  • Last Modified Date: 19 January 2017
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    Conjecture Corporation
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The fire triangle is an illustrative model used to show what elements are needed to start and sustain a fire. The three elements that make up the triangle are heat, fuel, and an oxidizer (usually oxygen). While this model is at times a bit simplistic, it helps explain, in an easy-to-understand way, how most fires are started and sustained.

The starting point of any fire, and one corner of the triangle, is the fuel source. Without fuel, there is no substance to burn. Almost all substances on earth can serve as a fuel source if exposed to enough heat, but the most common are class A and B fuels, such as wood, paper, gasoline, and propane. In order for a fuel source to catch fire, two things must be present: enough oxygen to start and sustain the fire, and either a specific ignition source or a high enough ambient temperature to ignite the fuel.

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Once a fire has started, as long as enough fuel and oxygen are present, the heat generated by the fuel source continues the combustion process in lieu of the original ignition source. The self-sustaining nature of fire is what makes it so dangerous and difficult to extinguish. When a fire gets too far out of control, sometimes extinguishing it is no longer a possibility and it must be left to burn out on its own. Due to the sheer size of forest fires, wildland firefighters must often cut down huge swathes of trees and clear away great amounts of underbrush in order to stop the fire from spreading, thereby depending on the fire to run out of fuel on its own.

In order to extinguish a burning fire, at least one of the elements of the fire triangle must be removed. There are different methods used for extinguishing different types of fires, but the most common way is to deprive the fire of oxygen with the use of a fire extinguisher. Most fire extinguishers spray a dry chemical, monoammonium phosphate, that melts on contact with the fuel source and cuts off oxygen by smothering it. The usually orange and red flames seen are not the source of a fire's heat and only a byproduct, which often causes confusion when someone is trying to put out a fire. Many people make the mistake of targeting the visible flames and not the actual fuel source when trying to put out a fire.

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anon952734
Post 4

Throwing water on a fire puts the heat out of a fire which takes away something from the fire triangle.

donasmrs
Post 3

@SarahGen-- I believe water takes away the oxygen and heat components of a fire. It absorbs the heat and smothers the burning object limiting its access to oxygen. That's why water turns into steam when it comes in touch with fire.

From my experience, depending on the size of the fire, water is not always very effective. A lot of water is required to put out fire if it's a large one. I think a blanket or a fire extinguisher works faster by immediately removing oxygen from the triangle.

SarahGen
Post 2

How does throwing water on a burning object disrupt the fire triangle?

fBoyle
Post 1

This is why when forests catch fire in the summer, they continue for days on end unless something is done about it.

I hear about forest fires every year, especially during summertime. The fire usually starts with a burning cigarette or a piece of glass that attracts heat from the sun. Pine trees are especially inclined to fires because they burn easily and the fires quickly spread.

These kind of fires almost always require intervention with helicopters or they will wipe out thousands of acres.

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